MXPA00006163A - Zeolite l catalyst in a furnace reactor - Google Patents

Abstract

A process for catalytic reforming of feed hydrocarbons to form aromatics, comprising contacting the feed, under catalytic reforming conditions, with catalyst disposed in the tubes of a furnace, wherein the catalyst is a monofunctional, non-acidic catalyst and comprises a Group VIII metal and zeolite L, and wherein the furnace tubes are from 2 to 8 inches in inside diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes.

Description

ZEOLITE L CATALYST IN AN OVEN-REACTOR FIELD OF THE INVENTION The present invention relates to the catalytic conversion using a catalyst comprising a large pore, monofunctional, non-acidic zeolite, and a Group VIII metal, which has a low deactivation or fouling ratio and provides high aromatics. More particularly, the present invention relates to the use of such a catalyst in furnaces that are fired with gas or oil.

BACKGROUND OF THE INVENTION The various reactions encompass conversions such as dehydrogenation, isomerization, dehydroisomerization, cyclization and dehydrocyclization. In the process of the present invention, aromatics are formed from hydrocarbons fed or supplied to the conversion reaction zone, and dehydrocyclization is the most important reaction.

REF: 121168 U.S. Patent No. 4,104,320 by Bernard and Nury, discloses that it is possible to dehydrocycline paraffins to produce aromatics with high selectivity using a monofunctional non-acidic zeolite type L catalyst. The catalyst based on L zeolite at 320 has interchangeable cations of which at least 90% are sodium, lithium, potassium, rubidium or cesium, and contain at least one noble metal of Group VIII (or tin or germanium). In particular, the catalysts having platinum in potassium form the zeolite L exchanged with a salt of rubidium or cesium, were claimed by Bernard and Nury to achieve exceptionally high selectivity for the conversion of n-hexane to benzene. As described in the Patent of Bernard and Nury, L zeolites are typically synthesized in the potassium form. A portion, -usually not more than 80%, potassium cations can be exchanged, so that other cations replace the exchangeable potassium.

Recently, an additional important step was discovered in U.S. Patent Nos. 4,434,311; 4,435,283; 4,447,316; and 4,517,306 by Buss and Hughes. The Patents of Buss and Hughes disclose catalysts comprising a large pore zeolite exchanged with an alkaline earth metal (barium, strontium or calcium, preferably barium), which contains one or more Group VIII metals (preferably platinum) and its use in the conversion of petroleum gasoline. As an essential element in the catalyst is the alkaline earth metal. Especially when the alkaline earth metal is barium, and the large pore zeolite is zeolite L, the catalyst was found to still provide higher selectivities than the corresponding alkalies exchanged with the zeolite L catalysts, described in US Pat. No. 4, 104, 230. These catalysts of. high selectivity of Bernard and Nury, and Buss and Hughes, are all "non-acidic" and are referred to as "monofunctional catalysts". These catalysts are highly selective for aromatic conversions via dehydrocyclization of paraffins. Having discovered a highly selective catalyst, commercialization was seen as promising. Unfortunately, this was not the case, because high-selectivity L zeolite catalysts do not reach a sufficiently long run length to make them feasible for use in catalytic conversion. U.S. Patent No. 4,456,527 describes the surprising finding that if the sulfur content of the feed or feed is reduced to ultra low levels, below the levels used in the past for catalysts especially sensitive to sulfur, then the long run lengths could be achieved with the non-acidic catalyst of zeolite L. Specifically, it was found that the concentration of sulfur in the hydrocarbon fed or supplied to the catalyst zeolite L, should be at ultra low levels, preferably less than 100 parts per billion (ppb), more preferably, less than 50 ppb, to achieve the stability / improved activity of the catalyst used. It was also found that the conversion catalysts of zeolite L, they are surprisingly sensitive to the presence of water, particularly while under reaction conditions. Water has been found to greatly accelerate the deactivation ratio of these catalysts. U.S. Patent No. 4,830,732, which is incorporated herein by reference, describes the surprising sensitivity of zeolite L catalysts to water and the ways to mitigate the problem.

U.S. Patent No. 5,382,353 and U.S. Patent No. 5,620,937 to Mulas ey et al., Which is incorporated herein by reference, discloses an L-zeolite based on conversion catalysts wherein the catalyst is treated at a high temperature and at a low content of water to thereby improve the stability of the catalyst, that is, to decrease the rate of deactivation of the catalyst under conversion conditions. During the commercialization of the zeolite L conversion catalysts, it was found that ultralow sulfur levels cause an unexpected problem of coking, carburization and dusting of the metallurgy of the reactor system. This problem has required the use of special steels and / or steels that have protective layers to prevent coking, carburization and dusting of the metal. When used, the protective layers on steel surfaces are contacted or in contact with the hydrocarbons at process temperatures, for example, at temperatures between about 800-1150 ° F. For example, a protective layer of tin has been used in reactors and furnace tubes of a catalytic conversion operated at ultra low sulfur levels. This has effectively reduced the rate of external coke formation in the catalyst particles in the reactors. Without this protection, the accumulation of coke could have resulted in a massive coke clogging and shutdown or shutdown of the reactor system. These problems are described in detail in Heyse et al., US 5,674,376. Heyse et al, describes the use of special steels and protective coatings, including tin covers, to prevent carburization and dusting of the metal. In a preferred embodiment, Heyse et al., Shows the application of a tin paint to a steel portion of a reactor system and the heating in hydrogen to produce an intermetallic layer resistant to carburization containing iron and nickel stanides. The conversion system of Heyse et al., Is a high temperature, low sulfur and low water system that uses a conventional conversion design, that is, furnaces to heat the food or supply and catalysts located in conventional reactors. Recently, several patents and patent applications of RAULO (Search Association for the Use of Light Oil) and Idemitsu Kosan CO., Have been published regarding the use of halogen in monofunctional conversion catalysts based on zeolite L. Such halogens contain monofunctional catalysts have been reported to have improved stability (catalyst life) when used in catalytic conversion, particularly in the conversion feeder materials that boil above the C7 hydrocarbons in addition to the hydrocarbons Ce and C. In this regard, see EP 201,856A; EP 498,182 A; U.S. Patent Nos. 4,681,865; and U.S. Patent No. 5,091,351. EP 403,976 by Yoneda et al., And assigned to RAULO, describes the use of catalyst based on zeolite Z treated with fluorine in tubes of small diameters of approximately one inch in internal diameter (22.2 mm to 28 mm in the examples). The heating medium proposed for the small tubes were fused metals or fused salts to maintain similar control of the temperature of the tubes. Accordingly, EP 403,976 does not show the use of a conventional type of furnace or conventional type of furnace tubes. Conventional furnaces for catalytic conversion have tubes usually three or more inches in internal diameter (76 mm or more), while EP 403,976 discloses that the use of tubes having an inner diameter greater than 50 mm is undesirable. Also, conventional ovens are heated using ovens that are fired with gas or oil. The typical catalytic conversion process uses a series of conventional furnaces to heat naphtha feedstocks, before each conversion stage in the reactor, as the conversion reaction is endothermic. Thus, in a three stage conversion process, the total conversion unit may comprise a first furnace, followed by a first reactor vessel stage containing the conversion catalyst (on such a catalyst, the endothermic conversion reaction occurs); a second furnace followed by a second reactor stage containing conversion catalyst on which the conversion reaction further progresses; and a third furnace, followed by a third reactor stage with the catalyst to further progress the conversion levels of the conversion reaction. "For example, U.S. Patent No. 4,155,835 to Antal illustrates a three-stage conversion process, with three ovens (30, 44, 52) and three conversion reactors (40, 48, 56) shown in the drawing in Antal. The example conversion reactors used in accordance with the prior art are shown, for example, in U.S. Patent No. 5,211,837 by Russ et al., Particularly the radial flow reactor of Russ et al., Shown in Figure 2. In some catalytic conversion units, as many as five or six furnace states, followed by reactors, are used in series for the catalytic conversion unit, in particular, the conversion of hydrocarbons on a zeolite L Pt catalyst in a highly reactive reaction. endothermic and may require as many as 5 or 6 stages or more of furnaces, followed by reactors The present invention allows such a multi-stage process to greatly simplify to two or more preferably, a reactant. r of oven.

BRIEF DESCRIPTION OF THE INVENTION In accordance with a preferred embodiment of the present invention, a process is provided for the catalytic conversion of hydrocarbons fed or supplied. The process comprises passing hydrocarbons over a catalyst comprising a Group VIII metal and a large pore zeolite placed inside a furnace, wherein said furnace comprises a first chamber and a second enclosed chamber separated by a heat exchange surface, in wherein the catalyst is located within said first chamber and one or more burners are located within said second chamber. Preferably, the catalyst is not more than 4 inches from the heat exchange surface and at least one portion of the catalyst is not more than one inch from the heat exchange surface. A preferred embodiment of the process comprises contacting the food or feed, under catalytic conversion conditions, with a catalyst placed in tubes of an oven, wherein the catalyst is a monofunctional, non-acidic catalyst and comprises a Group VIII metal and zeolite L, and wherein the furnace tubes are 2 to 8 inches in internal diameter, and wherein the furnace tubes are heated, at least in part, by gas or oil burners located outside the furnace tubes. In a preferred embodiment of the present invention, the furnace may be basically a conventional type furnace, except that the catalyst is placed in the furnace tubes and the metallurgy of the reactor is constructed to avoid carburization and metal dusting problems caused for the low sulphurous environment. The furnace is heated by conventional means by the naphtha conversion units, such as by gas burners or oil burners. Also in the present invention, the size of the tubes is conventional, in the range of 2 to 8 inches, preferably 3 to 6 inches, more preferably 3 to 4 inches, of inner diameter. The monofunctional L-zeolite-based catalyst is contained within the tubes of the conventional furnace according to a particularly preferred embodiment of the present invention. In a particularly preferred embodiment, the furnace tubes are made of a material having a carburization resistance and metal dusting under low sulphurous conversion conditions at least as large as the stainless steel type 347. The furnace tubes can be: (a) made of type 347 stainless steel or a steel that has a carburization and metal dusting resistance at least as large as stainless steel type 347; or (b) treated by a method comprising plating, plating, painting or coating the surfaces of the furnace tube to contact the food or supply to improve the carburization and dusting resistance of the metal; (c) constructed of, or aligned with, a ceramic material. Among other factors, the present invention is based on my unexpected conception and finding that, using the catalysts defined herein, particularly conversion catalysts based on monofunctional, non-acidic large pore zeolite, the rearrangement or conventional rearrangement of the ovens and reactors of multi-stage conversion, can be combined in one or more stages of conventional ovens, eliminating the downstream of the vessels of the furnace conversion reactor. In one embodiment of the present invention, the defined monofunctional conversion catalyst is disposed in the tubes of a conventional furnace. A preferred embodiment of the present invention is also based on my finding that a conversion arrangement of conventional multi-stage reactors / furnaces (consisting of, for example, three or six, or as many as nine stages of furnaces and reactors) can be replaced by a few as a basically conventional oven that contains monofunctional L zeolite conversion catalysts in the furnace tubes. The present invention is also based on the discovery that zeolite catalysts of improved stability (i.e., which have a deactivation ratio of less than 0.04 degrees F per hour at conversion conditions) can be effectively and economically used in a reactor furnace for catalytic conversion. The improved stability of these catalysts also allows them to be used at operating conditions that allow catalyst regeneration of frequent or continuous long run lengths. My intention allows for simplified process schemes and significantly less capital equipment than conventional catalytic conversion systems. In an alternate embodiment of the present invention, the furnace may be constructed such that the burners are located within the tubes located in the furnace and the catalyst located in the area surrounding the tubes. The area containing the catalyst can be an individual chamber or a multitude of chambers. In such rearrangements or rearrangements, no portion of the catalyst that must be more than 4 inches from the tube surface has been found for reasons of heat flow. Catalysts that are more than 4 inches from the heated surface can not be effective in the dehydrocycling of hydrocarbons due to the highly endothermic nature of the dehydrocyclization reactions and the dependence on heat flow in the distance from the burner tube or heat exchange surface. More preferably, the catalyst should not be more than 3 inches from a burner tube surface. Even more preferably, the catalyst should not be more than 2 inches from a surface of the burner head. It has also been found that there are preferably one or more inches of the catalyst package around the burner tubes and more preferably, 1.5 or more inches of the catalyst package around the surface of the burner tube. This reduces the amount of heat exchange surface in the reactor furnace and helps minimize the number of furnace-reactors required for the conversion. In yet another embodiment of the present invention, the reactor furnace comprises two or more chambers. One or more chambers contain burners. One or more attached chambers contain the catalyst. The number of chamber (s) and the attached chamber (s) of the catalyst are separated by an effective surface to provide heat exchange. This surface between the burner chamber or chambers and the catalyst chamber is referred to herein as the heat exchange surface. Cameras can have a variety of forms. It is important, however, that the catalyst should preferably be no more than 4 inches from a heat exchange surface for reasons of heat flow. The catalyst that is greater than the preferred distance of the heated surface, can not be effective to the dehydrocyclization of the hydrocarbons due to the highly endothermic nature of the dehydrocyclization reactions and the dependence of heat flow in the distance from the surface of heat exchange. Thus the catalyst that is greater than 4 inches from the heat exchange surface, can be effectively wasted. When I stated that the catalyst is not greater than an effective distance from the heat exchange surface to avoid waste of the catalyst means that at least 80% of the catalyst will be within the distance of the heat exchange surface, preferably at less 85% of the catalyst, more preferably at least 90%, still more preferably, at least 95% and more preferably, essentially all the catalysts are within the declared distance from the heat exchange surface. As stated above, I found that for the catalyst of the present invention, the catalyst should preferably not be more than 4 inches from the heat exchange surface. More preferably, the catalyst must not be more than 3 inches from the heat exchange surface. Still more preferably, the catalyst should not be more than 2 inches from the heat exchange surface. It has also been found, that it is preferably greater than one, and more preferably 1.5 or more inches of the catalyst package around the heat exchange surface. This reduces the amount of heat exchange surface in the furnace-reactor and helps minimize the number of furnace-reactors required for the conversion. As listed in the Background, U.S. Patent No. 4,155,835, illustrates the use of a three-stage conversion unit, comprising three conventional ovens, and three conversion reactor vessels containing the catalyst, with one downstream located reactor from each of the three ovens. In contrast, the present invention combines or collapses furnaces and separates the reactors in one or more furnace tube reactor system, without separate reactor vessels. In accordance with the present invention, preferably, the system is only a furnace tube reactor, that is, the coalescence or combination to a furnace. I found that the present invention is particularly advantageously carried out at relatively low hydrocarbon hydrogen or feed mole ratios of 0.5 to 0.3, preferably 0.5 to 2.0, more preferably 1.0 to 2.0, more preferably 1.0 to 1.5. on a molar basis. I found that high spatial velocities can be used in the process of the present invention. Preferred space velocities are 1.0 to 7.0 volumes of feed or supply per hour per volume of catalyst, more preferably 1.6 to 6 hours-1, and still more preferably 3 to 5 hours-1. The ratio of mol of food or supply of hydrogen to relatively low hydrocarbon and high space velocities, when used in the present invention, make feasible the use of fewer total catalysts and at a lower total gas flow rate. These benefits, in turn, allow the use of a reactor furnace with a reasonable number of tubes. Preferably, the Group VIII metals used in the catalyst placed in the furnace tubes, comprise platinum, palladium, iridium and other Group VIII metals. Platinum is more preferred as the Group VIII metal in the catalyst used in the present invention. Also, the preferred catalysts for use in the present invention are non-acidic zeolite 1 catalysts, wherein the interchangeable ions of the zeolite L, such as sodium and / or potassium, have been exchanged with ferrous alkali or alkali metals. A particularly preferred catalyst is the zeolite L Pt Ba, wherein the zeolite L has been exchanged using a solution containing barium. These catalysts are described in more detail in the Bus and Hughes references cited above in the Background section, in which the references are incorporated by reference, particularly as the description of the zeolite catalyst L Pt. In accordance with another preferred embodiment of the present invention, the L-zeolite-based catalyst is produced by treatment in a gaseous medium in a temperature range between 1025 ° F and 1275 ° F, while maintaining the water level in the effluent gas below 1000 ppm. Preferably, the high temperature treatment is carried out at a water level in the effluent gas below 200 ppm. The high temperature treated catalysts are described in the Mulasky et al patents, cited above in the Background section, in which the references are incorporated herein by reference, particularly as the description of zeolite catalysts L Pt, treated at high temperatures . According to another preferred embodiment of the present invention, the zeolite-based catalyst contains at least, a halogen in an amount between 0.1 and 2.0% by weight, based on zeolite L. Preferably, the halogens are fluorine and chlorine and are present in the catalysts in an amount between 0.1 and 1.0% by weight of fluorine and 0.1 and 1.0. % by weight of chlorine at the start of the run. Preferred halogen-containing catalysts are described in the RAULO and IKC patents cited above in the Background section, in which references are incorporated herein by reference, particularly as the description of halogen-containing L-Pt zeolite catalysts. The aforementioned halogens can be added to the ex situ catalyst for example, when the catalyst is made or can be added in situ, for example at the start of the run. The preferred halogen contents of the aforementioned catalyst should preferably be present in the catalyst at the start of the Run, when the food or feed is introduced into the catalyst under conversion conditions. Preferred foods or supplies for the process of the present invention are the hydrocarbons boiling range naphtha, that is, boiling hydrocarbons within the range of paraffins and naphthenes C6 to C or more preferably in the range of paraffins and naphthenes C6 to Cs, and more preferably paraffins and naphthenes Ce to C7. The feedstock may contain minor amounts. of boiling hydrocarbons out of the specified range, such as 5 to 20%, preferably, only 2 to 7% by weight. There are several different paraffins from each of the various carbon numbers. Consequently, it will be understood that the boiling point has some rank or variation at a given cut-off point of carbon number. Typically, the food or paraffin-rich supply is derived by the fractionation of a crude petroleum oil. In a preferred embodiment of the present invention, the supply contacting the catalyst preferably contains less than 50 ppb of sulfur, more preferably less than 10 ppb of sulfur. In the present invention, the ratios of low catalysts are important. Ultra-low sulfur in the feed or supply contributes to the success of the present invention. Two patents that approximately show the need to avoid sulfur poisoning of zeolite L Pt catalysts and show how to achieve ultra-low sulphurous conditions are U.S. Patent Nos. 4,456,527 and 5,322,615, which are incorporated herein by reference. In one embodiment of the present invention, the furnace tubes are filled with. catalyst, and a conventional tube is associated with the tubes is used as a means of combination of heating and catalytic reaction medium. In a particularly preferred embodiment of the present invention, the catalyst is selected to have a particularly low deactivation rate, under conversion conditions. Preferably, the catalyst selected for use under the selected reaction conditions are such that the deactivation ratio of catalyst is controlled at less than 0.04 ° F per hour, more preferably less than 0.03 ° F, still more preferably less than 0.02 ° F, and more preferably less than 0.01 ° F per hour, at an aromatic yield of 50% by weight, using a feed or supply of C6-C7UDEX raffinate at a liquid space velocity per hour of 4 hours-1, and a mol ratio. of hydrogen to hydrocarbon of 2. Using a catalyst and conditions having particularly low deactivation ranges allow less catalyst, be used in the reactor furnace and allow the use of large diameter tubes. In another embodiment of the invention does not use tubes, the catalyst may also be far from a heat exchange surface than when using a catalyst having a high deactivation ratio. This in turn, allows the total length of the tubes or in an alternate mode to the heat exchange surface area, be minimized and made economical to replace the multitude of furnace / reactor loops (usually, 3-6 or more reactors in a conventional Lt zeolite catalyst reformer) with an individual furnace-reactor. The present invention can again be contrasted with U.S. Patent No. 4,155,835 to Antal. The Antal reference uses reformer reactor vessels separate from conventional ovens, while the present invention does not. In addition, although the Antal process reduces sulfur to very low sulfur levels in the feed or supply, as low as 0.2 ppm sulfur, the present invention is preferably carried out at sulfur levels greater than an order of magnitude below, such as below of 10 ppb of sulfur in the feed or supply to the catalyst based on monofunctional L zeolite contained in the furnace-reactor system of the present invention. The preferred conversion conditions for the reactor furnace of the present invention using the preferred catalyst comprises a monofunctional L zeolite that includes an LSHV between 1.5 and 1.6; a hydrogen to hydrocarbon ratio between 0.5 and 3.0; and a heat exchange surface temperature for reagents (indoor temperature) between 600 ° F and 960 ° C at the entrance and between 860 ° F and 960 ° F at the start of the Run (SOR), and between 600 ° F and 1025 ° F at the entrance and between 920 ° F and 1025 ° F at the exit and End of the Run (EOR). The EOR is the time at which the run is completed, usually due to deactivation of the catalyst. The catalyst of the present invention is considered to EOR to a point when the outlet temperature is not greater than 1025 ° F. BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a schematic flow chart for a furnace tube reactor system. Figure 2 is an aerial cross-sectional view of a furnace tube reactor system showing the burners (X) and the reactor tubes (o). Figure 3 is a simplified diagram showing a vertical cross section with gas-fired heaters (shaded) adjacent to the parallel series of furnace tubes containing the catalyst. Figure 4 shows cross-sectional views of alternate embodiments of furnace-reactor systems showing the burners (X) and the catalyst chamber (s) as aerial transverse areas.

DETAILED DESCRIPTION OF THE DRAWINGS The drawings shown here are, only for descriptive purposes of possible embodiments of the invention, and are not proposed in any way to limit the invention. Figure 1 is a schematic flow chart for a furnace tube reactor system. The hydrocarbon is supplied to the line through the unit (1). The sulfur content of the hydrocarbon is reduced to desired low levels in the sulfur control unit (2). The hydrocarbon then enters via line (3) to an optional heat exchanger or preheater (4). The optionally heated effluent enters via line (5) to the reactor furnace (6) where it is simultaneously heated and brought into contact with the catalyst. The reactor effluent then between the line (7) to a light gas stabilizer is removed from the stabilizer by the line (8) and the liquid product leads to the stabilizer by line (9), which enters the distillation of the product ( not shown). Figure 2 is an aerial cross-sectional view of a furnace tube reactor system showing the burners (X) and the reactor tubes (o). The reactor tubes are filled with the catalyst. This is only a possible rearrangement of the furnace tube. Figure 3 is a simplified diagram showing a vertical cross section with a gas fired heater adjacent to a parallel series of furnace tubes containing the catalyst. Figure 4 shows cross-sectional views of alternate embodiments of furnace-reactor systems showing the burners (X) and the catalyst chamber (s) as transverse hatched areas. There are numerous other possible furnace-reactor configurations. The four arrangements in Figure 4 are only meant as illustrations of possible embodiments of the configurations of the chamber employed in the reactor furnace of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The catalyst used in the process of the present invention comprises a Group VIII metal and zeolite L. The catalyst of the present invention is a non-acidic monofunctional catalyst. The Group VIII metal of the catalyst of the present invention is preferably a noble metal, such as platinum or palladium. Platinum is particularly preferred. Preferred amounts of platinum are 0.1 to 5% by weight, more preferably 0.1 to 3% by weight and more preferably 0.3 to 1.5% by weight, based on zeolite L. In the present application, the terms "L zeolite" and " Zeolite L "are used simultaneously to refer to the LTL type zeolite. The zeolite L component of the catalyst is described in the published literature, such as in U.S. Patent No. 3,216,789. The chemical formula for zeolite L can be presented as follows: (0.9-1.3) M2 / nO: Al2O3 (5.2-6.9) Si02: yH20 wherein M designates a cation, n represents the valence of M, and Y can be any value from about 0 to about 9. The zeolite L, its X-ray diffraction pattern, its properties and methods for its preparation, are described in detail in U.S. Patent No. 3,216,789. Zeolite L has been characterized in "Zeolite Molecular Sieves" by Donald W. Breck, John Wile and Sons, 1974, (reprinted in 1984) that has a frame that includes cancrinite cages of unit of 18 tetrahedra, linked by six double rings in columns and reticulated by simple oxygen bridges to form rings of 12 flat elements. The sorption pores of the hydrocarbon for zeolite L are reported approximately 7 in diameter. Breck's reference and U.S. Patent No. 3,216,789 are incorporated herein by reference, particularly with respect to their description of zeolite L. The various zeolites are generally defined in terms of their diffraction patterns with X-rays. Several factors have an effect on the X-ray diffraction pattern of a zeolite. Such factors include temperature, pressure, size of crystals, impurities and type of cations present. For example, when the crystal size of the L-type zeolite becomes more sticky, the X-ray diffraction pattern sometimes becomes larger and less precise. Thus, the term "zeolite L" includes any of the various zeolites made from cancrinite cages having an X-ray diffraction pattern substantially equal to the X-ray diffraction patterns shown in U.S. Patent No. 3,216,789. L-type zeolites are synthesized in conventional form in the form of potassium, that is, in the theoretical formula previously given; more than M cations are potassium. The M cations are interchangeable such that a given L-type zeolite, for example, an L-type zeolite in the "potassium form," can be used to obtain the L-type zeolites containing other cations by subjecting the L-type zeolite to an ion exchange treatment in an aqueous solution of an appropriate salt or salts, however, it is difficult to exchange all the original cations, for example, potassium, since some cations in the zeolite are in sites that are difficult to • reach for the reactants. The preferred L zeolites for use in the present invention are those synthesized in the potassium form.

Preferably, the zeolite L in the potassium form is ion exchanged to replace a portion of the potassium, more preferably with an alkaline earth metal, the barium is an alkaline earth metal especially preferred for this purpose as previously established.

The catalysts used in the process of the present invention are monofunctional catalysts, meaning that they do not have the acid function of conventional reforming catalysts. Traditional or conventional reforming catalysts are bifunctional, because they have an acid function and a metallic function. Examples of bifunctional catalysts include platinum and acid alumina as described in U.S. Patent No. 3,006,841 to Haensel; platinum-rhenium on acidic alumina as described in U.S. Patent No. 3,415,737 to Kluksdahl; platinum-tin on acid alumina; and platinum-iridium with bismuth on an acid carrier as described in US Patent No. 3,878,089 to Wilhelm (see also the other bismuth-containing acid catalysts, cited above in the Background section). Examples of monofunctional catalysts include platinum on zeolite L, wherein the zeolite L has been exchanged with an alkali metal, as described in U.S. Patent No. 4,104,320 to Bernard et al .; platinum on zeolite L, wherein the zeolite L has been exchanged with an alkaline earth metal, as described in US Pat. No. 4,634,518 to Buss and Hughes; platinum on zeolite L, as described in US Patent No. 4,456,527 to Buss, Field and Robinson; and platinum on halogenated L zeolite, as described in the RAULO and IKC patents cited above. According to another embodiment of the present invention, the catalyst is an activated or reduced catalyst (HTR) at an elevated temperature. Preferably, the pretreatment process used on the catalyst occurs in the presence of a reducing gas such as hydrogen, as described in U.S. Patent No. 5,382,353 issued January 17, 1995, and U.S. Patent Application 08 / 475,821 , which are expressly incorporated as a reference in their entirety. Generally, contact occurs at a pressure from 0 to 300 psi gauge and a temperature from 1877 ° C to 2372 ° C (1025 ° F to 1275 ° F) for 1 hour to 120 hours, most preferably for at least 2 hours , and most preferably by at least 4-48 hours. Most preferably, the temperature is from 1922 ° C to 2282 ° C (1050 ° F to 1250 ° F). In general, the length of time for pretreatment will sometimes be dependent on the final treatment temperature, with the highest final temperature being shorter than the treatment time that is necessary. For a commercial size plant, it is necessary to limit the moisture content of the environment during the high temperature treatment to prevent deactivation of the significant catalyst. In the temperature range from 2435.4 ° C to 2327 ° C (1025 ° F to 1275 ° F), the presence of moisture is believed to have a severely detrimental effect on catalyst activity. Therefore, it has been found necessary to limit the moisture content of the environment for as little water as possible during the treatment period, for at least. less than 200 ppmv, preferably less than 100 ppmv of water. In one embodiment, to limit the exposure of the catalyst to water vapor at high temperatures, it is preferred that the catalyst be initially reduced at a temperature between 540 ° C and 1292 ° C (300 ° F and 700 ° F). After most of the water generated during the reduction of the catalyst has been shrouded from the catalyst, the temperature rises slowly in the ramp form or in staggered form at a maximum temperature between 1877 ° C to 2372 ° C (1025 ° F) and 1250 ° F). The temperature prm and the gas flow rates should be selected to limit the water vapor levels in the reactor effluent to less than 200 ppmv and, preferably, less than 100 ppmv when the temperature of the catalyst bed exceeds 1877 ° C (1025 ° F). The ratio of temperature increased to the final activation temperature will typically be averaged between 41 ° C and 122 ° C (5 and 50 ° F) per hour. Generally, the catalyst will be heated at a rate between 50 ° C and 77 ° C (10 and 25 ° F) per hour. It is preferred that the gas flow through the catalytic bed during this process exceed 500 volumes per volume of catalyst per hour, where the volume of the gas flow is measured at standard conditions of one atmosphere and 140 ° C (60 ° F) . In other words, the volume of gas flow is greater than 500 space volumes per hour of gas (for its acronym in English, GHSV). GHSVs in excess of 5000 per hour will normally exceed the capacity of the compressor. GHSVs between 600 and 2000 per hour are more preferred. The pretreatment process occurs prior to the contact of the reforming catalyst with a hydrocarbon feed. The largest pore zeolitic catalyst is generally treated in a reducing atmosphere in the temperature range from 1877 ° C to 2372 ° C (1025 ° F to 1275 ° F). Although other reduction gases can be used, dry hydrogen is preferred as a reduction gas. The hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally varying from 1% to 99% by volume. More typically, however, the amount of hydrogen in the mixture varies from about 10 to 50% by volume. In another embodiment, the catalyst can be pre-treated using an inert gaseous environment in the temperature range from 1877-2372 ° C (1025-1275 ° F), as described in US Patent Application No. 08 / 450,697, filed on 25 May 1995, which is expressly incorporated herein by reference in its entirety. The preferred inert gas is nitrogen, for reasons of availability and cost. However, other inert gases can be used such as helium, argon, and krypton or mixtures thereof. Accordingly, a particularly preferred embodiment of the present invention, the monofunctional, non-acidic catalyst used in the process of the present invention contains a halogen. This can be confusing at first, because halogens are frequently used to contribute to the acidity of alumina supports for bifunctional, acidic reforming catalysts. However, the use of halogens with catalysts based on zeolite L can be done while retaining the monofunctional, non-acid characteristics of the catalyst. Methods for producing L-zeolite-based catalysts containing non-acidic halogen are described in the references of RAULO and IKC cited above in the Background section. The term "non-acidic" is understood by those skilled in the art, particularly by the contrast between monofunctional (non-acidic) reforming catalysts and bifunctional (acidic) reforming catalysts. A method for achieving non-acidity is by the presence of alkali metals and / or alkaline earth metals in the zeolite L, and preferably it is achieved, together with another improvement of the catalyst, by exchange of cations such as sodium and / or potassium from the zeolite L synthesized using alkaline or alkaline earth metals. Preferred alkali or alkaline earth metals for such exchanges include potassium and barium. The term "non-acid" also connotes the high selectivity of the catalyst for the conversion of aliphatics, especially paraffins, to aromatics, especially benzene, toluene and / or xylenes. The high selectivity includes at least 30% selectivity for the formation of aromatics, preferably 4.0%, more preferably 50%. The selectivity is the percentage of the conversion leading to aromatics, especially to BTX (Benzene, Toluene, Xylene) aromatics when an aliphatic feed of 6 to 8 carbon atoms is fed. Preferred feeds for the process of the present invention are naphthas of 6 to 9 carbon atoms. The catalyst of the present invention has an advantage with paraffinic feeds, which normally provide poor aromatics produced with conventional bifunctional reforming catalysts. However, naphthenic feeds are also easily converted to aromatics on the catalyst of the present invention. More preferably, the feeds to the process of the present invention are naphthas of 6 to 7 carbon atoms. The furnace-reactor system of the present invention is particularly advantageously applied to convert naphthas of 6 to 7 carbon atoms to aromatics. Particularly preferred catalytic reforming conditions for the present invention include, as described above under the Brief Description of the Invention, an LHSV between 1.5 and 6.0-1, a hydrogen to hydrocarbon ratio between 0.5 and 2.0, a reagent temperature between 1112 ° C and 1877 ° C (600 ° F and 1025 ° F), and an outlet pressure between 35 and 75 psig. Preferably, the catalyst used in the process of the present invention is linked. The bond of the catalyst improves its resistance to breakage, compared to an unbound catalyst comprising platinum on zeolite L powder. Preferred binders for the catalyst of the present invention are alumina or silica. Silica is especially preferred for the catalyst used in the present invention. Preferred amounts of binders are from 5 to 90% by weight of the finished catalyst, more preferably from 10 to 50% by weight, and even more preferably from 10 to 30% by weight.

When the catalyst can be bound or unbound, the weight percentages provided are based on the L zeolite component of the catalyst, unless otherwise indicated. The term "catalyst" as used herein in a broad sense includes the final catalyst as well as precursors of the final catalyst. The precursors of the final catalyst include, for example, the unbound or bound form of the catalyst and also the catalyst prior to final activation by reduction. The term "catalyst" is thus used to refer to the activated catalyst in some contexts here, and in other contexts to refer to forms of catalyst precursors, as will be understood by experts from the context. Also with respect to the use of the halogenated form of the monofunctional catalyst in the present invention, the halogen in percent in the catalyst is that at the start of operation (for its acronym in English, SOR). During the course of the operation or use of the catalyst, some of the halogens are usually lost from the catalyst.

A furnace tube reactor system of the preferred embodiment of the present invention relates to a reforming system in which the highly selective, non-acidic zeolite-based catalyst L is contained within a plurality of furnace tubes. conventional ones which are themselves contained within the furnace. See Figure 1 which shows a schematic diagram of a furnace-reactor reforming process. The furnace tubes are preferably parallel to each other and are preferably arranged vertically. Typically, the furnace tube rows alternate with rows of burners. Figures 2 and 3 show a suitable arrangement for the burners and furnace tubes. Figure 2 shows a horizontal cross-section of the furnace-reactor of the preferred embodiment wherein Xs designates burners and Os designate tubes. Figure 3 shows a longitudinal view of the furnace tube reactor of the preferred embodiment where the burners are shown making downward impact parallel to the tubes. The tubes are preferably 5.08 to 20.32 cm (2 to 8 inches) in diameter, most preferably from 7.62 to 15.24 cm (3 to 6 inches) in diameter, and most preferably from 7.62 to 10.16 c (3 to 4). inches) in diameter, and can be up to 156.6 cm (45 feet) long. The furnace tubes are preferably less than or equal to 914.4 cm (3 feet) long and preferably are at least 304.8 cm (10 feet) long. The arrangement of the furnace tubes and burners may vary. Thus, the furnace tubes can be placed vertically, or horizontally, or in a serpentine or shaft arrangement or in a helical serpentine arrangement. The burners may also be oriented in a number of different ways, for example in the lower part of the furnace that points to or on the side of the furnace that is pointing horizontally. Preferably, the furnace tubes are placed vertically with the burners pointing downwards parallel to the tubes. The furnace-reactors can be linked in series or in parallel, but preferably the system is designed such that a single furnace reactor is used. The replacement of the 3 to 6 or more conventional reformer reactors and furnace circuits in a L Pt zeolite reformer with a single furnace-reactant is preferable and is feasible with a zeolite catalyst L Pt having high activity and a high speed of slow deactivation. It has been found that the replacement of a plurality of conventional reactors and furnace circuits results in greatly reduced investment costs for the zeolite reformer L Pt. In a preferred embodiment, the use of vertical tubes filled with catalyst, the feed enters the top of the tubes The burners are mounted on the roof of the furnace burning down in the firebox. The maximum heat flow could then be at point e where the feed enters the furnace tubes, which is desirable. Alternatively, a multi-zone oven can be used. Here the flow of heat can be varied in a more controllable way. The flow of heat supplied to the reactor inlets is preferably larger than that applied near the outlet of the reactor. It is desirable that the surfaces of the furnace tube or the heat exchange surfaces which contact the hydrocarbons and which are aromatic, are made of a material having a carburization resistance and the metal dust remover at least as large as that of the 347 stainless steel type under the conditions of low sulfur reformation. The resistance to carburation and dedusting of the metal can be easily determined using the procedure outlined below in Example 4. In a preferred embodiment of the invention, the furnace tube reactors are made of (a) stainless steel 347 or a steel having a resistance carburetion and dedusting of metal at least large ta such as stainless steel 347; or (b) the furnace tubes are treated by a method that includes plating, metallic coating, painted coated surfaces to make contact with 'Feeding to provide improved resistance to metal carburation and dedusting; (c) the furnace tubes are constructed of or coated with a ceramic material. More preferably, the furnace tubes are constructed of a 300 series steel type provided with an intermetallic coating on the surfaces that contact hydrocarbons. In one embodiment of the invention, the furnace tubes have a coating containing metal, metallic, silver, or painted coating applied to at least a portion (preferably at least 50%, more preferably at least 75% and most preferred for all) of the area of the surface that is to be contacted with hydrocarbons at the conversion temperature. After coating, the metal-lined reactor system is preferably heated to produce intermetallic and / or metal carbide layers. A preferred metal-lined reactor system preferably comprises a base construction material (such as a carbon steel, a chromium steel, or a stainless steel) having one or more adherent metal layers bonded thereto. Examples of metal layers include elemental iron-tin and chromium intermetallic compounds, such as FeSn. As used herein, the term "metal-containing coating" or "coating" is intended to include metal coatings, plating, paints and other coatings containing either elemental metals, metal oxides, organometallic compounds, metal alloys, mixtures of these components and similar. The metal or metal compounds (s) are preferably a key component (s) of the coating. Fluid paints that can be sprayed or brushed are a preferred type of coating. In a preferred embodiment, the coated steel is heat treated to produce intermetallic compounds, thereby reacting the coating metal with the steel. Especially preferred metals are those which interact with, and preferably react with, the base material of the reactor system to produce a continuous, adherent metallic protective layer at lower temperatures or at the proposed hydrocarbon conversion conditions. The metals that melt further down or to the conditions of the reforming process are especially preferred that they can more easily provide full coverage of the substrate material. These metals include those selected from tin, antimony, germanium, arsenic, bismuth, aluminum, gallium, indium, copper, lead, and mixtures, intermetallic compounds and alloys thereof. Preferred metal-containing coatings comprise metals selected from the group consisting of tin, antimony, germanium, arsenic, bismuth, aluminum, and mixtures, intermetallic compounds and alloys of these metals. Especially preferred coatings include tin, antimony and germanium coatings. These metals will form continuous and adherent protective layers. Tin coatings are especially preferred - they are easy to apply to steel, inexpensive and environmentally benign. It is preferred that the coatings be sufficiently thick that they completely cover the base metallurgy and that the resulting protective layers remain intact during years of operation. For example, tin paints can be applied at a thickness (fresh) of between 1 to 6 mils, preferably between about 2 to 4 mils. In general, the thickness after curing is preferably between about 0.1 to 50 mils, more preferably between about 0.5 to 10 mils. Metal-containing coatings can be applied in a variety of forms, which are well known in the art, such as electroplating, chemical vapor deposition, and electronic or crackling, to name a few. Preferred coating application methods include painted and plated. Where practical, it is preferred that the coating be applied in a formulation similar to paint (later referred to as "painting"). Such a paint can be sprayed, applied by brush, or in a dirty form, etc., on the surfaces of the reactor system. A preferred protective layer is prepared from a paint containing metal. Preferably, the paint comprises or produces a reactive metal that interacts with the steel. Tin is a preferred metal and is exemplified here; the description here around tin, is generally applicable to other metals such as germanium. Preferred paints comprise a metal component selected from the group consisting of: a metal compound which can be decomposed by hydrogen such as an organometallic compound, finely divided metal and a metal oxide, preferably a metal oxide which can be reduced at procedure or furnace tube. In a preferred embodiment the curing step produces a metallic protective layer bonded to the steel through an intermediate bonding layer, for example a carbide-rich bonding layer, as described in US Patent No. 5,674,376, which is incorporated here for reference in its entirety. This patent also describes the coating and paint formulations. The tin protective layers are especially preferred. For example, a tin paint can be used. A preferred paint contains at least four components or their functional equivalents: (i) a tin compound which can be decomposed by hydrogen, (ii) a solvent system, (iii) a finely divided tin metal and (iv) tin. As the tin compound can be decomposed by hydrogen, organometallic compounds such as octanoate or tin neodecanoate are particularly useful. Component (iv), tin oxide is a porous tin-containing compound which can absorb the organometallic tin compound, and can be reduced to metallic tin. The paints preferably contain finely divided solids to minimize sediment. The finely divided tin metal, component (iii) above, is also added to ensure that the metallic tin is available to react with the surface to be coated at as low a temperature as possible. The particle size of the tin is preferably small, for example one to five microns. Tin in the form of metal stanides (for example, iron stanides and nickel / iron stanides) is then heated under reducing conditions, for example in the presence of hydrogen. In one embodiment, a tin paint containing stannic oxide, metallic tin powder, isopropyl alcohol and 20% Tin Ten-Cem (produced by Mooney Chemical Inc., Cleveland, Ohio) can be used. Twenty percent of Tin Ten-Cem contains 20% tin as stannous octanoate in octanoic acid or stannous neodecanoate in neodecanoic acid. When tin paints are applied in proper consistency, the conditions of reduction under heating will result in migration to cover small regions (eg, gualda) that are not painted. This will completely cover the metal base. Additional information on the composition of the tin protective layers is described in U.S. Patent No. 5,406,014 to Heyse et al., Which is incorporated herein by reference. Here it is taught that a double layer is formed when the tin is covered with a layer rich in chromium, steel containing nickel. Both a chromium-rich inner layer and an outer layer of stannium are produced. The outer layer contains nickel stanides. When a tin paint was applied to a type 304 stainless steel and heated to about 2192 ° C (1200 ° F), it resulted in a chromium-rich steel layer containing approximately 17% chromium and substantially no nickel, comparable to 430 degree stainless steel. Tin / iron paints are also useful in the present invention. A preferred steel / iron paint will contain various tin compounds to which the iron has been added in amounts in excess of one third of Fe / Sn by weight. The addition of iron can, for example, be in the form of F0203. The addition of iron to a paint containing tin could provide significant advantages; in particular: (i) it could facilitate the reaction of the paint to form iron stanols, thus acting as a flow; (ii) it could dilute the nickel concentration in the stannide layer thereby providing a coating having a better protection against coking; and (iii) it could result in a paint that provides the anti-coke protection of the iron stanides even if the fundamental surface does not react well.

Some of the coatings, such as the tin paint described above, are preferably cured, for example, by heat treatment. Curing conditions depend on the particular coating metal and cure conditions that are selected to produce an adherent protective layer. The gas flow rates and the contact time depend on the curing temperature used, the coating metal and the specific components of the coating composition. The coated materials are preferably cured in the absence of oxygen. If they are not initially in the metallic state, they are preferably cured in a reducing atmosphere, preferably a hydrogen-containing atmosphere, at elevated temperatures. The curing conditions depend on the coating metal and are selected such that they produce a continuous and uninterrupted protective layer that adheres to the steel substrate. The resulting protective layer is able to remain in the repeated temperature cycle, and is not degraded in the reaction environment. Preferred protective layers are also useful in reactor systems that are subjected to oxidation environments, such as those associated with the separation by burning of the coke. In general, contacting the reactor system having a coating containing metal, platinum, metallic coating, paint or other coating applied to the portion thereof with hydrogen is depleted for a sufficient time and temperature to produce a protective layer metallic These conditions can be easily determined. For example, the coated checkbooks can be heated in the presence of hydrogen in a simple test apparatus, the formation of the protective layer can be determined using petrographic analysis. It is preferred that the curing conditions result in a protective layer that is firmly attached to the steel. This can be done, for example, by curing the coating applied at high temperatures. The metallic or non-metallic compounds contained in the paint, plating, metallic coating or other coating are preferably cured under conditions effective to produce metals and / or molten compounds. Accordingly, germanium and antimony paints are preferably cured between 1832 ° C (1000 ° F) and 2552 ° C (1400 ° F). The tin paints are preferably cured between 1652 ° C (900 ° F) and 2012 ° C (1100 ° F). Healing is preferably depleted over a period of hours, often with temperatures increasing all the time. The presence of hydrogen is particularly advantageous when the paint contains reducible oxides and / or organometallic compounds containing oxygen. As a suitable example of a paint cure for a tin paint, the system including the painted portions can be pressurized with nitrogen flow, followed by the addition of a hydrogen-containing steam. The reactor inlet temperature can be raised to 1472 ° C (800 ° F) at a rate of (122-212 ° C) ° C / hr (50-100 ° F / hr). Then the temperature can be raised to a level of 1742-1787 ° C (950-975 ° F) at a rate of 122 ° C / hr (50 ° F / hr), and stay within the range of about 48 hours.

The Oven Tube Construction Material There is a wide variety of base construction materials that can be used in furnace tubes or heat exchanger surfaces. If the tubes / surfaces are to be protected with a metallic coating, then a wide range of steels can be used. In general, steels are chosen to meet the requirements of strength and flexibility for catalytic reforming processes. These requirements are well known in the art and depend on the process conditions, such as operating temperatures and pressures. Useful steels include carbon steel; steels of low alloys such as chrome steel 1.25, 2.5, 5, 7, and 9; stainless steels of the 300 series including 304, 316 and 346; heat-resistant steels including HK-40 and HP-50, as well as treated steels such as chrome or aluised steels. Preferred steels include stainless steels of the 300 series and heat resistant steels. Depending on the components of the metal-containing coating, the reaction of the steel with the coating may occur. Preferably, the reaction results in an intermediate bond rich in carbide or "sticky" layer that is fixed to the steel and does not easily peel or flake off. For example, metallic tin, germanium and antimony (if applied directly as a platinum or metallic coating or produced in situ) readily react with the steel at elevated temperatures to form a bonding layer as described in US Patent No. 5,406,014 or WO 94/15896, both of Heyse et al. The '014 patent is incorporated herein for reference in its entirety. If the pipes / surfaces are not protected with a metallic coating, they can be protected against carburation and the metallic dusting with a ceramic coating. These types of coatings are well known in the art. See U.S. Patent 4, 161, 510. Furnace tube reactors may also be constructed of uncoated steels, provided the steels have a carburizing and metal removal strength at least as large as 347 stainless steel under the conditions of low sulfur reformation. See later Example 4. Useful steels include stainless steel series 300 including stainless steels of type 304, 316 and 347; heat resistant steels including HK-40 and HP-50, as well as treated steel such as aluminized or chrome steels. As stated at the beginning, it has also been found that in the process of the present invention, high spatial speeds are advantageously used. The relatively high space speeds allow to decrease the total volume of the tube to be used. Lower space velocities or relationships require more tube volume to contain the proper amount (desired) catalyst and thus may be less desirable, particularly if - the total size of the furnace must be significantly larger to accommodate the increased volume of tubes. The diameter and length of the furnace tubes can be varied so that a desired pressure drop and heat flow through the tubes is achieved. The length and diameter of the furnace tubes, and the location and number of burners, allow to regulate the temperature of the skin or cover of the furnace tubes as well as the radial and axial temperature profile of the furnace tubes. These parameters can be designated to allow the proper conversion of particular feeds. However, the concept of the present invention requires that the furnace be basically conventional. Accordingly, the size of the furnace tubes will be at least 5.08 cm (two inches) in internal diameter, most preferably at least 7.62 cm (three inches) in internal diameter. Also, the furnace will be heated by conventional means, such as burners ignited by gas or oil.

The pressure drip across the length of the furnace tubes is preferably less than or equal to 70 psi, more preferably, less than 60 psi, most preferably less than 50 psi. The outlet pressure is preferably between 25 and 100 psig, more preferably between 35 and 75 psig, and most preferably between 40 and 50 psig. The outlet pressure is the pressure of the reaction mixture at the outlet of the furnace tubes, such as the tubes and in the contained reaction mixture that comes out of the furnace. For a more complete understanding of the present invention, the following examples illustrating certain aspects of the invention are set forth. It should be understood that, however, the invention is not intended to be limited in any way to the specific details of the examples.

EXAMPLES Example 1 This example compares a conventional adiabatic multi-stage reactor system with the externally heated oven tube reactor of the present invention. The catalyst used in this comparison is a platinum or halogenated zeolite L as described in the IKC patents cited early. The total volume of the catalyst in the two systems is the same. The same light naphtha is used as feed or supply to both reactor systems. The food or supply of light naphtha contains 2 percent Cs, 90 percent Ce (mainly paraffins, but also smaller amounts of naphthalenes), and 8 percent by volume of C7. The conditions in the example have been adjusted to give the same total run length for the two systems in comparison.

This example shows that, in accordance with the concept of the present invention, a conventional externally heated single oven can effectively replace a multi-reactor reactor system of six reactors, with a catalyst placed in the furnace tubes. The present invention also provides a substantially increased aromatic yield. The increase in yield results in more aromatics produced during the run. Alternatively the furnace holding reactor can be operated at decreased severity allowing a much lower deactivation rate for a given yield thus allowing a running length substantially longer than one year. We have found that this result can be accompanied in the reactor system of the furnace tube of the present invention at a lower peak catalyst temperature against the use of multi-stage adiabatic reactors with conventional ovens preceding each of the stages of the reactor.

Example 2 This example compares a conventional adiabatic multi-stage reactor system with the externally heated oven tube reactor of the present invention. The catalyst used in this comparison is a platinum or halogenated zeolite L, as described in the RAULO and IKC patents cited early. The total volume of the catalyst in this example in the furnace tube reactor is greater than in the first example and the total volume of the catalyst is twice as much as in the first example. The total volume of the catalyst in the two systems compared is the same (1170 cubic feet). same. The same light naphtha is used as feed or supply to both reactor systems. The conditions and parameters in the example have been adjusted to give the same total run length for the two systems in comparison. The food or supply ratio of the two systems is also the same.

This example shows that for a decrease in catalyst activity at a lower space velocity than the previous example, in accordance with the concept of the present invention, a single reactor furnace with a catalyst placed in the furnace tubes can be effectively replaced in a multi-reactor reactor system of six reactors. This example also shows that there are substantially better aromatics yields using the furnace-reactor. The increase in yield results in more aromatics produced during the run. Alternatively the furnace holding reactor can be operated at decreased severity allowing a much lower deactivation rate for a given yield thus allowing a running length substantially longer than one year.

Example 3 In the following example, a reduced high temperature catalyst is used in an externally heated furnace tube reactor and compared with the use of the same HTE catalyst in an adiabatic multi-stage reactor system.

This example illustrates that, a multi-reactor reactor system of six reactors can be effectively replaced by a system in accordance with the present invention, wherein the catalyst is placed in the tubes of a single externally heated conventional oven. The catalyst used in this example is a reduced high temperature catalyst comprising Pt in zeolite L. This example has an increased aromatic yield. This result is accompanied by a lower peak catalyst temperature in the externally heated oven reactor system than in the system comprising several ovens and reactors separated in series.

Example 4 To determine the resistance of various substrates to the coking, carburation and dusting of the metal under ultra-low sulphide conversion conditions, the following tests can be run. The test makes it particularly easy to make face-to-face comparisons, for example comparisons with the stainless steel type 347. The test uses a Lindberg quartz tube furnace, with temperatures controlled within a degree with a thermo pair placed on the outside of the furnace in the heated zone. The furnace tube has an internal diameter of 5/8 inches. Several preliminary test runs are conducted at an applied temperature of 1200 ° F, using a thermo pair suspended within the hot zone of the tube. The internal thermo pair constantly measures up to 10 ° F less than the external thermo pair. Samples of steel and other construction materials are then tested at 1100 ° F, 1150 ° F and 1200 ° F for 24 hours, and at 1100 ° F for 90 hours, under conditions that stimulate the exposure of materials under sulphurous conversion conditions. low. Samples of various materials should be clean and free of rust, grease or oxidation stains. The samples compared should be equally soft. Samples are placed in an open quartz vessel or vessels within the hot zone of the furnace tube. Containers or vessels are 1 inch per foot and also within the hot zone of two inches of the tube. The vessels or vessels are attached to the silica glass rods for easier placement and removal. An internal thermo pair is not used when the boats are placed inside the tube. Prior to the beginning, the test materials are cut to a size and shape suitable for visual identification easier. After a pre-treatment, such as calcination, the samples are weighed. Most samples weigh less than 300 mg. Typically, each run is conducted with three to five samples in a boat. A sample of 347 stainless steel is present in each run as an internal standard. After the samples are placed, the tube is flooded with a sulfur-free nitrogen for a few minutes. A carburizing gas from a commercially bottled 7% propane mixture in hydrogen, it is pumped through a one liter flask of high purity toluene at room temperature to enter approximately 1% toluene in the feed gas mixture. This carburizing gas contains less than 10 ppb of sulfur. Gas flows of 25 to 30 cc / min, and atmospheric pressure, are maintained in the apparatus. The samples are brought to operating temperatures at a rate of approximately 100 ° F / minute. After exposure of the materials to the carburizing gas for the desired time and temperature, the apparatus is cooled rapidly with a current of air applied to the outside of the tube. When the apparatus is sufficiently cold, the hydrocarbon gas is flushed with nitrogen and the ship is removed for inspection and analysis. After the completion of each run, the condition of the boat and each material is carefully noted. Typically, the ship is photographed. Then, each material and its associated coke and dust is weighed to determine the changes. Care is taken to keep some coke deposited with the appropriate substratum material. The samples are then mounted on an epoxy resin, cemented and polished in preparation for the petrographic microscopic and electron scanning analysis. The degree of corrosion of the surface is determined; this indicates the response of the dusting of the metal and the carburation of each material. In general, a qualitative visual analysis of the reactivities of the metal is easily done. The residence time of the carburizing gas used in these tests is considerably higher than in the typical commercial operation. Thus, it is believed that the test conditions may be more severe than the commercial conditions. Indeed, the test provides an effective indication of the relative strength of the materials for carburizing and sprinkling the metal.

Example 5 - Preparation of Tin-Coated Steel The pieces of 321 SS were coated with a paint containing tin. The paint consists of a mixture of 2 parts of powdered tin oxide, 2 parts of fine powdered tin (1-5 microns), 1 part of stannous neodecanoate in neodecanoic acid (20% of Tim-Cem Tin manufactured by Mooney Chemical Inc., Cleveland, Ohi, which contains 20% tin as a stannous neodecanoate) mixed with isopropanol, as described in US 5,674,376. The cover was applied to the steel surface by painting and awarding the air dried paint. After drying, the painted steel is contacted with hydrogen gas at 1100 ° F for 24 hours. The resulting coated steel specimens with intermetallic steel layers are visually examined by the complementation of the cover. Also, the cross-sections assembled and polished of the materials when examined using pectrographic and scanning electron microscopy. Micrographs show that tin paint has tin reduced to metallic under these conditions. A continuous and adherent metallic protective layer (iron / is nickel tannin) was observed on the steel surface. These techniques show that tin intermetallic compounds, including stanols containing iron and nickel, were present at a thickness of between 2 to 5 microns. A lower layer consumed nickel with a thickness of approximately 2-5 microns was also presented. If the cure is made at a lower temperature, this lower layer is not formed.

Example 6 - Analysis of Steel Samples of coated cured steels and preferably heat cured steels were shown in a clear epoxy resin and then ground and polished in preparation for analysis with petrographic and electron scanning microscopy (SEM). The samples were analyzed before and after the removal conditions. The EDX analysis can be used to determine the chemical composition of the layers. For example, intermetallic tin layers can be analyzed by iron, nickel and tin.

Example 7 Determination of the deactivation ratio of a catalyst The deactivation ratio of a catalyst sample used in the present invention can be determined in an isothermal pilot plant or similar unit under the following standard conditions using a standard food or feed. The feed or supply to the unit should be a C6-C7 UDEX raffinate from a conventional reformer. The UDEX refined supply will have the following composition as measured by Gas Chromatography; a Ce paraffin content of 39 to 43% by weight, a total Cs content of 45 to 50% by weight, a total Ci content of 35 to 35% by weight, a total C5 content of 5 to 11% by weight, and a total Ce content of less than 6% by weight. The supply must contain less than 10 ppb of sulfur, and less than 3 ppm of water. The pilot plant should be free of any other possible source of sulfur contamination. Care should be taken to avoid sulfur contamination of the system and avoid using a previously contaminated sulfur system. Two patents showing how to clean up to a sulfur-contaminated system are US Pat. Nos. 5,035,792 and 4,940,532, both of which are incorporated herein by reference. The LHSV of the unit should be placed at (1 / hour) with a pressure system of 85 psig. The hydrogen / hydrocarbon mole ratio of the system should be 2. The pilot plant unit should be operated at a temperature sufficient to maintain the aromatics in the reactor effluent at 50% by weight. The temperature is increased to maintain 50% by weight of the aromatics and the results plotted over a period of 8 weeks (1344 hours) of stable continuous operation under said conditions. The proportions of fouling or fouling can be determined by the period of stable operation by the division of the change in temperature over the period by the number of hours.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (24)

CLAIMS Having described the foregoing, the property contained in the following claims is claimed as property:

1. A process for the catalytic conversion of hydrocarbons supplied or fed to form aromatics, characterized in that it comprises, contacting the supply under catalytic conversion conditions, with a catalyst placed in the tubes of an oven, wherein the catalyst is a non-acidic catalyst , monofunctional and comprising a Group VIII metal and L zeolite, and wherein the furnace tubes are 2 to 8 inches in internal diameter, and wherein the furnace tubes are heated, at least, in part, burners gas or oil located outside the furnace tubes.

2. A process for the catalytic conversion of hydrocarbons, characterized in that it comprises: passing hydrocarbons on a catalyst comprising a Group VIII metal and an L zeolite, located inside a furnace; wherein said furnaces comprise a first chamber and a second adjacent chamber separated by a heat exchange surface; wherein said catalyst is located within said first chamber and one or more oil or gas burners are located within the second chamber; and wherein the catalyst is not more than 4 inches from the heat exchange surface, and at least, a portion of said catalyst is greater than one inch from the heat exchange surface.

3. The process according to claim 1, characterized in that the catalyst under the conversion conditions has a deactivation ratio of less than 0.04 degrees F per hours.

4. The process according to claim 2, characterized in that the catalyst under the conversion conditions has a deactivation rate of less than 0.04 degrees F per hours.

5. A process according to claim 1, characterized in that the furnace tubes are 3 to 6 inches in diameter.

6. The process of claim 2, characterized in that the catalyst is not more than 3 inches from the heat exchange surface and at least one portion of said catalyst is greater than 1.5 inches from the heat exchange surface.

7. A process according to claim 1 or 2, characterized in that the catalytic conversion conditions include an LHSV of 1.0 to 7.

8. A process according to claim 1 or 2, characterized in that the catalytic conversion conditions include a ratio of hydrogen to hydrocarbon mole of between 0.5 and 3.0.

9. A process according to claim 1 or 2, characterized in that the Group VIII metal is platinum.

10. A process according to claim 1 or 2, characterized in that the catalyst is produced by stages comprising, treatment in a gaseous environment in a temperature range between 1025 ° F and 1275 ° F, while maintaining the water level in the effluent gas below 1000 ppm.

11. A process according to claim 10, characterized in that the water level is below 200 ppm.

12. A process according to claim 1 or 2, characterized in that the catalyst contains at least one halogen in an amount between 0.1 and 2.0% based on zeolite L.

13. A process according to claim 12, characterized in that the halogens and fluorine and chlorine are present in the catalyst in an amount of between 0.1 and 1.0% by weight of fluorine, and 0.1 and 1.0% by weight of chlorine at the beginning of the run.

14. A process according to claim 1 or 2, characterized in that the supply contains less than 50 ppb of sulfur.

15. A process according to claim 13, characterized in that the supply contains less than 10 ppb of sulfur

16. A process according to claim 1 or 3, characterized by the conditions of catalytic conversion include an LSHV between 3 and 5, a hydrogen to hydrocarbon ratio between 1 and 1.5, an internal temperature of the furnace tube between 600 ° F and 960 ° F at the entrance and between 860 ° F and 1025 ° F at the exit to SOR and between 600 ° F and 1025 ° F at the entrance and between 920 ° F and 1025 ° F at the exit to EOR, and an exit pressure between 35 and 75 psig.

17. A process according to claims 1 to 3, characterized in that said furnace tubes are made from a material having a carburation resistance and a metal dusting below the sulphurous conversion conditions at least as large as the type 347 stainless steel.

18. A process according to claims 2 to 4, characterized in that said first chamber is made of a material having a resistance to carburation and sprinkling of the metal under catalytic sulphide conversion conditions at least as large as those of steel type 347 stainless.

19. A process according to claims 1 to 3 characterized in that: (a) said furnace tubes are made of type 347 of stainless steel or a steel having a resistance to carburization and dusting of the metal at least, as large as the type 347 stainless steel; or (b) said furnace tubes have been treated by methods comprising plating, plating, painting or coating the surfaces of the furnace tube to contact the food or supply to improve the carburizing and dusted resistance of the metal; or (c) said furnace tubes are constructed of or aligned with a ceramic material.

20. A process according to claim 2 or 4, characterized in that: (a) said first chamber is made of type 347 of stainless steel or a steel having a resistance to carburization and sprinkling of the metal at least as large as type 347 stainless steel; (b) said first chamber has been treated by a method comprising plating, chapping, painting or reverting the surfaces of the first chamber to contact the supply or food to provide improved resistance to carburation and sprinkling of the metal; or (c) said first chamber is constructed of or aligned with a ceramic material.

21. A process according to claim 2, characterized in that the catalytic conversion conditions include an LSHV between 3 and 5, and a hydrogen to hydrocarbon ratio between 1.0 and 1.5.

22. The process of claims 1 or 2, characterized in that the catalyst under the conditions of said conversion has a deactivation ratio of less than 0.03 degrees F per hour.

23. The process of claims 1 or 2, characterized in that the deactivation rate is less than 0.02 degrees F per hour.

24. The process of claims 1 or 2, characterized in that the deactivation rate is less than 0.01 degrees F per hour.